Here are my modifications. First, I made some modifications to the chest, torso, thighs and rear of the model. You can see those pictures here.
I then modified the shoulders and upper arms, which you can see here. This was inspired by CX52J's initial design, although I went in a bit of a different direction.
Here's a shot of where I'm at now. I need to order some 1x2 technic bricks in dark red in order to replace the blue pins with black ones, and I need a few extra parts to complete the pauldrons.
I tried that last night, although I didn't take any pictures of it. The head that is 4 studs wide is way too small. The one that is included is six studs wide and is only a little bit too big. I think that a head that was 5 studs wide would be great, but unfortunately this doesn't actually exist.